Views:248 Author:Site Editor Publish Time: 2020-12-01 Origin:Site
Line accident refers to the sudden interruption of overhead power distribution due to various reasons. After an accident occurs, only when the accident point and the type of accident are identified can the cause of the accident be found and emergency repair measures can be taken to restore the normal operation of the overhead power lines and prevent future similar accidents.
Common overhead electric line faults include overhead distribution line wind skew flashover, lightning trip, lightning breakage, line icing fault, line pollution flashover, line external force damage, line bird damage, etc.
1. Failure caused by wind
The operating environment of overhead lines is relatively complicated. Many of the overhead lines are in complex mountainous terrain. At the same time, the overhead lines are long. Various conditions may be encountered in the sections of the road, such as mountains, sand dunes, traffic trunks, etc., so that if there is a strong wind, this part of the overhead line will sway directly under the action of the wind load, resulting in the occurrence of wind flashover. At the same time, when the wind load occurs, it will pose a certain threat to the tower with long service life, breaking the balance of the original tower or causing the tower to collapse. Some transmission lines are near trees. When these trees continue to grow, they break the safe distance from the transmission line. Once strong winds occur, short circuit and earth fault will occur. Therefore, the impact of strong wind on the overhead power distribution line is very serious, and the consequences are very serious. Moreover, once a power line failure occurs due to a wind disaster, it is difficult to solve it in a short time, which will lead to continuous losses.
2. Lightning trip
The overvoltage caused by thundercloud discharge in the power system is called lightning overvoltage. In this case, the remote overhead line fault passage indicator will work. Because its electromagnetic energy comes from outside the system, it is also called external overvoltage, and because thundercloud discharge occurs in the atmosphere, it is also called atmospheric overvoltage.
There are two kinds of common overvoltage in overhead power lines: the first is the induced overvoltage on the overhead line, that is, the overvoltage generated on the transmission line through electromagnetic induction when a lightning strike occurs near the overhead line; the second is direct strike lightning overvoltage, which refers to the overvoltage generated when lightning strikes the lightning protection wire directly.
There are three situations in which lightning strikes directly on the overhead line with lightning protection line: (1) Bypassing the lightning conductor and hitting the wire, that is, shielding. (2) Lightning strikes the top of the tower. (3) Lightning strikes the central part of the lightning protection line.
3. Line icing fault
At present, line icing can be classified from many angles. Under normal circumstances, according to the degree of damage and the requirements of power system operation, maintenance, design and scientific research, the line icing is divided into hoarfrost, rime, glazed frost and mixed rime. Rime is the most common form of icing on power lines in high-altitude mountainous areas in winter. Overhead power line icing accidents are related to the average annual number of rime days and annual average number of rime days. Generally speaking, the influence of the annual average number of rime days is more serious than the annual average number of rime days.
There are many cases causing faults on power lines, such as the short circuit to ground and the power short circuit, we need line fault indicators to find out information about the faults.